Mario Party 8 game screen problem.

Im new to this whole forum thing, but I need some help figuring something out. I went to play Mario Party 8 on my new widescreen television and when the game itself starts, the screen goes back to a standard square, it doesnt fill the whole screen. The opening of game, where I can choose what to play like battle or minigames, is normal, but the game itself is not. I tried changing it on my TV, but that wasn't working and is not the problem. Wondering if anyone knew a way to change the size of the screen through the actual game itself......?